Unsaturated cyanoaldehydes and method for their preparation



Patented Feb. 20, 1945 UNlTED STATES PATENT OFFICE asmooe UN SATURATED CYANOALDEHYDES AND METHOD FOR THEIR PREPARATION Herman A. Bruson and Thomas W. Riener, Philadelphia, Pa., assignors to The Resinous Products & Chemical Company, Philadelphia, Pa., a corporation of Delaware No Drawing. Application May 25, 1943, Serial No. 488,400

5 Claims.

This invention relates to unsaturated cyanoaldehydes and to a method for their preparation. More particularly it deals with new compounds having the formula:

| RCH: CH=COHO The reaction which occurs involves a molecular rearrangement and is summariz d by the following equation:

Typical alkaline condensing agents which can be used include the oxides, hydroxides, amides, hydrides, and alcoholates of the alkali metals, the alkali metals themselves, or strong nonmetallic bases such as, for example, quaternary ammonium hydroxides. Of these agents, potassium hydroxide, trimethyl benzyl ammonium hydroxide, and sodium hydroxide have been found to be very efficient for the purpose.

The quantity of alkaline condensing agent used is small, amounts of the order of 0.5% to 5% on the combined weight of the reactants being sufficient to catalyze the reaction. If the aldehydes employed, however, are old and, therefore, partially oxidized, it is necessary to add suflicient alkali to neutralize such acidity and then a small excess to maintain constant alkalinity throughout the course of the condensation. Consequently, the reaction mixture is advantageously tested from time to time to make certain it is always alkaline to litmus indicator.

The condensation can be carried out in the absence or in the presence of an inert solvent such as benzene, dioxane, or tertiary butyl al- VELCUO.

cohol; and water can be'used as a solvent for the alkali. The reaction is exothermic and is preferably controlled by cooling or by the rate of addition of one reactant to the others. Reaction occurs at temperatures as low as 0 C. in many cases and is greatly accelerated at temperatures from i5. C. to C.

Typical a,v-disubstituted crotonaldehydes of the formula:

which can be used for the purpose of this invention are those in which R is an alkyl group, such as methyl, ethyl, propyl, butyl, hexyl, etc., and

R is a hydrocarbon group selected from alkyl, aryl, aralkyl, or cycloalkyl groups, such as methyl, ethyl, propyl, butyl, phenyl, methyl phenyl, butyl phenyL, benzyl, cyclohexyl, methyl cyclohexyl, etc. The more important and more readily available of these sip-unsaturated aldehydes are those wherein Rand R are alkyl groups which may be the same or difierent. These are readily obtainable by condensing together two molecules of the same aldehyde or a molecule of each of two different aliphatic aldehydes by known methods involving aldolization and the elimination of water.

Among these are ol/Y-diGthYl crotonaldehyde, which is obtained from n-butyraldehyde by reaction with alkalies or acids, o y-dimethyl crotonaldehyde, v-di-butyl crotonaldehyde, a-methylv-ethyl crotonaldehyde, and their homologues.

The following examples illustrate this invention, the parts given being by Weight:

Example 1 Acrylonitrile (53 parts) was added dropwise during the course of twenty minutes to a stirred mixture consisting of 126 parts of a -diethyl crotonaldehyde, 126 parts of tertiary butyl alcohol, and 5 parts of methenolic 30% potassium hydroxide solution while the reaction temperature was maintained at 2 6-32 C. fI'he mixture was stirred thereafter for two hours at room temperature and was then acidified with dilute hydroehloric acid, washed, dried, and distilled in The main fraction (79 parts) distilled at l40-145 C./6 mm. Upon redistillatio-n it boiled at 138-141 C./6 mm. and formed a pale yellow oil, corresponding to the formula:

Example 2 Acrylonitr-ile (110 parts) was added dropwise during the course of ninety minutes to a rapidly stirred mixture consisting of 252 parts of 41,7- diethyl crotonaldehyde and arts of aqueous potassium hydroxide solution while the reaction mixture was maintained at 45-55 C. After all of the acrylonitrile had been added, the mixture was stirred for one hour longer at 45- C. It was then cooled and neutralized with dilute hydrochloric acid. The rproduct was washed with water, dried, and distilled in vacuo.

The 2-ethy1-2- (p-cyanoethyl) -3-hexena1-1 distilled over between 126 and C. at 4 mm. as a pale yellow oil in a yield of parts.

The products are of value as intermediates for the preparation of pharmaceuticals, insecticides, and resins.

This invention is a continuation-impart of copending application Serial No. 466,050, filed November 18, 1942.

We claim:

1. A process for preparing unsaturated cyanoethyl) -3-hexenal-1 which com rises aldehydes which comprises reacting acrylonitrile in the presence of an alkaline condensing agent with an a,'y-disubstituted crotonaldehyde in which the aand 'y-substituents are hydrocarbon groups.

2. A process for preparing unsaturated cyanoaldehydes which comprises reacting acrylonitrile in the presence of an alkaline condensing agent with an a, -dialky1 crotonaldehyde.

- 3. A process for preparing unsaturated cyanoaldehydes which comprises reacting acrylonitrile in the presence of potassium hydroxide with an a -dialkyl crotonaldehydel 4. A process for preparing Z-ethyl-Z-(fl-cyanoreacting acrylonitrile in the presence of potassium hydroxide with a,'y-diethyl crotonaldehyde.

5. As a new compound, 2-ethyl-2-(5-cyanoethyl -3-hexenal-1. I

HEDRMAN A. BRUSON. THOMAS W. RIENER. 

